You'd need to use a software tool (program) that surveys all hotspots in range and reports the channel each is broadcasting on. So if you see there are 2 other hotspots broadcasting on your router's channel, it's not an ISP issue and it would be a good idea to change your router to a less crowded channel.

Well, yours and 2 others make 3 on a channel, and that is enough to potentially cause noticeable interference. If possible, it's certainly worth checking and changing your router's WiFi broadcast channel (if possible- urban locations like NYC and London can make channel pollution hard to avoid).